1. Field of the Invention
The present invention relates to a connector of a high tension cable or cord for an ignition plug used in an ignition circuit and the method of manufacturing the same, more specifically to a connector for use with the ignition plug made by connecting one end of the high tension cord to one end section of a metal terminal and covering the end of the cord and the metal terminal with an insulating rubber cap through molding, thereby forming the connector.
2. Description of the Prior Art
A conventional connector for connecting a high tension cable or cord containing a conducting member to an ignition plug is generally described hereinafter. A connector comprises a metallic terminal and an insulating rubber cap. The high tension cable or cord is inserted at one end portion thereof into the connector with the insulating coating of the end portion of the high tension cord stripped to expose the end portion of the conducting member contained in the high tension cord. The exposed conducting member portion is folded over the surface of the cord coating or cover so as to come into contact with the inner surface of the metallic terminal when inserted therein. That portion of the metallic terminal is crimped to fixedly hold the end portion of the high tension cable or cord received therein. The other end of the metallic terminal forms a plug receiving portion for receiving the ignition plug. The cord end portion and metallic terminal are covered with an insulating rubber cap. The portion where the rubber cap and the high tension cord are joined is properly coated with an adhesive. Depending on circumstance, the exposed conducting member at the end portion of the high tension cord may be covered with a covering layer formed from an insulating or conducting material before the insulating rubber cap is provided.
In the conventional connector wherein the metallic terminal is inserted into the independently formed rubber cap with the joined portion between the high tension cord and the rubber cap coated with an adhesive after insertion, the adherence of the cord to the rubber cap depends mainly on the bonding strength of the adhesive, which causes some problems in the connector as follows:
(1) A slight pull will result in the connector being pulled out.
(2) As a result of the permanent compression strain of the rubber cap and the action of removing it from the ignition plug, the bonded sections are inclined to be separated, and disengagement of the cord and leakage easily occur.
(3) As a result of the action of inserting and removing the ignition plug, displacement readily occurs between the rubber cap and the high tension cable or cord. (4) In the exposed section of the conducting member, where it is not covered with an insulating or conducting material, an electrical discharge can occur from the exposed section of the conducting member to the metallic terminal, and the increase in temperature at the end portion of the cord reaches 120.degree. C. to 200.degree. C., so that the cord will be easily damaged by heat.
(5) Even in the case where the exposed section of the conducting member is covered with an insulating or conducting member, an air pocket can be easily created between the cover and the conducting member, and there is the problem of fire damage to the conducting member from an internal corona discharge.
As a means to eliminate this kind of problems, if a cap is formed directly around the metallic terminal and the high tension cord through molding rather than using an adhesive to mount a cap thereto, it is possible to markedly increase the bonding strength. However, in molding, in the case where a rubber material such as EPDM having high viscosity usually used in this field is utilized, it is necessary to use extremely high pressure during molding, so there is the danger that the metallic terminal and the cord will be damaged. In the case where a thermoplastic resin is used, the high tension cord, especially, is degraded by heat because the molding is carried out at extremely high temperatures. In the case where a thermosetting resin is used, it does not perform adequately as a cap because it becomes extremely hard after molding. For reasons such as these, the molding of a cap around the metallic terminal and high tension cord has not usually been carried out.